text: Two argon atoms are attracted together by van der Waals forces when far from each other. When they are close, electrostatic forces repel them. There is a balance point where the van der Waals force matches the opposing repelling force, where energy is at a minimum, represented as the trough in the graph of interaction energy versus distance. This distance is the ground state of the unexcited argon dimer. In a vibrating molecule, the distance between the atoms bounces backwards and forwards from one side of the trough to the other. Faster vibrations will force the state up to higher levels in the energy trough.  If the vibration is too much the molecule will break up. In a rotating molecule, the centrifugal force drags the atoms apart, but can still be overcome by the attractive force. But if the rotation is too much the atoms break apart.